The systems currently used to seal perforations have a fundamental flaw. They form a restriction in the well. This creates a problem should there later arise a need to seal other perforations further down in the well.
U.S. Pat. No. 4,069,573 (Rogers 1978) (reissued as RE 30,802 in 1981) discloses an invention entitled a “method of securing a sleeve within a tube”. This type of sleeve was developed to repair heat exchangers associated with nuclear power generation plants. The sleeves are positioned within the tube, and then expanded outwardly to engage the tube. In accordance with the teachings of the Rogers patent, the sleeves are expanded using hydraulics or by applying a compressive force to an elastomer material.
U.S. Pat. No. 4,793,382 (Szalvay 1988) discloses an assembly for repairing a damaged pipe. The Szalvay reference contains a discussion of the shortcomings of the prior art apparatus used to expand sleeves. Some of such apparatus leave components in the damaged pipe, thereby restricting subsequent fluid flow. Others of such apparatus must be repositioned and then re-expanded at intervals along the sleeve. The Rogers reference is criticized as not being suitable where a leak proof fit is necessary; as is the teaching of the Rogers reference of using the sleeve to expand the damaged pipe. The Szalvay reference addresses these shortcomings by advocating the use of shape memory alloy elements. None of the prior art references address how a sleeve might be installed at a distance of several miles down a hydrocarbon producing well to seal off perforated zones or possibly repair damaged sections of conduit.